1. Field of the Invention
The present invention relates to a method and apparatus for detecting agglomerates formed in a mixed phase container such as a fluidized-bed olefin polymerization reactor container, and to a method and apparatus for fluidized-bed olefin polymerization.
2. Description of the Related Art
It is well known in the art that a method of radiation is being used for detecting agglomerates formed in a mixed phase container, such as a fluidized-bed olefin polymerization reactor container (refer to Japanese Patent Publication No.62-28961). In the radiation method, a radiation source is placed in the center of the container and a plurality of radiation detectors are disposed around the container. In order to detect the existence and the size of agglomerates, the detectors detect density fluctuations in the mixed phase between the radiation source and the detectors by using the radiation.
Another method for detecting agglomerates in the mixed phase container, shown in Japanese Laid-open Patent Publication No.4-361150, employs an electrostatic capacitance detecting method. Means for detecting electrostatic capacitance is disposed on the inner wall of the mixed phase container. This method is based on detecting fluctuations of electrostatic capacitance, since the density (dielectric constant) of agglomerates is greater than that of the mixed phase. When the agglomerates as gel-like are formed and attached on the wall in the mixed phase container, the detecting means detects fluctuations in the electrostatic capacitance thereof. Therefore, the detecting means is able to monitor the state of agglomerates by measuring the amount of fluctuations in electrostatic capacitance.
Further, another method for detecting agglomerates employs a detecting rod having a strain detecting means in the mixed phase container, as shown in Japanese Laid-open Patent Publication No.10-36447. According to this method, it is possible to detect the existence and the size of agglomerates formed in the mixed phase container by detecting an amount of the strain generated in the detecting rod when agglomerates collide with the detecting rod.
However, the method described above employing radiation to detect agglomerates requires special attention. For example, a fluidized-bed olefin polymerization reactor container is generally an enormous container of roughly cylindrical shape having a diameter of several meters and a height of several tens of meters. A worker must enter the container to remove the blockage when blockage occurs, or to perform the inspections at periodic inspections. Accordingly, since a radiation source is present in the container, sufficient considerations must be made to ensure the safety of workers performing such operations.
While the method employing an electrostatic capacitance detecting means to detect agglomerates is suitable for detecting agglomerates adhered to the inner walls of the container and has no problem related to safety, the method is not sufficiently precise for detecting agglomerates which are moving within the container. Further, since the difference between the density of small agglomerates and that of normal olefin polymer product is small, this method is not sufficient even for detecting agglomerates adhered to the inner walls of the container.
The method of detecting agglomerates using a strain detecting device does not have the problems described above. However, in this method, it is essential that the agglomerates effectively collide with the detecting rod. Since the agglomerates formed in the container move along with the flow of gas and powders such as products of the olefin polymer and/or catalysts in the mixed phase, it is necessary to know beforehand how gas and powders in the mixed phase will flow. Or else, agglomerates will not collide with the detecting rod with an effective force, thereby greatly lowering the sensitivity of detection.
If the detecting rod and the direction in which gas and powders flow form a right angle or obtuse angle, agglomerates moving along with the flow of gas and powders may get caught and accumulate on the part of the detecting rod facing with the flow. If agglomerates adhere to the detecting rod in this way, not only it is impossible to precisely detect the agglomerates, but also the accumulating agglomerates actually block detection of other agglomerates in the container. As the agglomerates accumulate further, it is very likely that the accumulation will obstruct fluidization in the container and promote further agglomeration.
The present invention has been made in view of the above drawbacks. It is an object of the present invention to provide a safe method and apparatus capable of detecting even small agglomerates with a high degree of precision and sensitivity and without obstructing fluidization within the mixed phase container. It is another object of the present invention to provide a method and apparatus for fluidized-bed olefin polymerization.
According to an aspect of the present invention, there is provided a method for detecting agglomerates in a mixed phase container by measuring strain in a detecting rod disposed in the mixed phase container in which a mixed phase of gas and powders is formed, wherein the detecting rod is disposed at an insertion angle in the range from 20 degrees to 70 degrees, preferably from 25 degrees to 50 degrees, with relation to the flow of gas and powders. This method can prevent the agglomerates formed in the mixed phase container from accumulating on the part of the detecting rod facing with the flow.
According to another aspect of the present invention, there is provided a method for detecting agglomerates, wherein a distributor plate specially designed to swirl gas and powders above the plate (referred to as distributor plate hereinafter) is disposed on the bottom of the mixed phase container for diffusing the gas in a horizontal direction, and the detecting rod is positioned at a predetermined height above the distributor plate. This method can control the flow of gas and powders within the mixed phase container, thereby effectively forcing the agglomerates to collide with the detecting rod.
According to another aspect of the present invention, there is provided an apparatus for detecting agglomerates in a mixed phase container by strain detecting means in a detecting rod disposed in the mixed phase container in which a mixed phase of gas and powders is formed, wherein the detecting rod is disposed at an insertion angle in the range from 20 degrees to 70 degrees with relation to the flow of gas and powders. This arrangement can prevent the agglomerates formed in the mixed phase container from accumulating on the part of the detecting rod facing with the flow more effectively.
According to another aspect of the present invention, there is provided an apparatus for detecting agglomerates, wherein a distributor plate is disposed on the bottom of the mixed phase container for diffusing the gas in a horizontal direction, and the detecting rod is positioned at a predetermined height above the distributor plate. This arrangement can control the flow of gas and powders within the mixed phase container, thereby effectively forcing the agglomerates to collide with the detecting rod.
According to another aspect of the present invention, there is provided a fluidized-bed olefin polymerization reactor wherein a mixed phase of gas and powders is formed, the reactor comprising an apparatus for detecting agglomerates in the mixed phase, the apparatus having a detecting rod for measuring strain when the agglomerates collide thereto, wherein the detecting rod is disposed at an insertion angle in the range from 20 degrees to 70 degrees with relation to the flow of gas and powders.
According to another aspect of the present invention, there is provided an olefin polymerization method, comprising: detecting agglomerates in a mixed phase container by measuring strain in a detecting rod disposed in the mixed phase container in which a mixed phase of gas and powders is formed, wherein the detecting rod is disposed at an insertion angle in the range from 20 degrees to 70 degrees with relation to the flow of gas and powders; and removing the agglomerates from the mixed phase container.
According to another aspect of the present invention, there is provided a method for manufacturing an olefin polymer, said method comprising: detecting agglomerates in a mixed phase container by measuring strain in a detecting rod disposed in said mixed phase container in which a mixed phase of gas and powders is formed, wherein said detecting rod is disposed at an insertion angle in the range from 20 degrees to 70 degrees with relation to the flow of the gas and powders; and removing said agglomerates from said mixed phase container.
The above and other objects, features, and advantages of the present invention will be apparent from the following description when taken in conjunction with the accompanying drawings which illustrates preferred embodiments of the present invention by way of example.